outlook crashes when opening shared mailbox

The other scenario is mailbox delegation from ECP.

One is OWA delegation, in this case, the delegated user logs in as Delegated which does not grant access to the mailbox's email either in OWA or in Outlook. There are two primary ways to establish delegated access to a mailbox. That's why we ended up deleting the group and going with a shared mailbox Whitcher

We couldn't get external email delivered to the group, and after searching through the documentation I discovered that is a known issue with this configuration. Unfortunately, we have a hybrid exchange environment configured with centralized mail flow. We had initially tried creating this mailbox as an O365 Group, which it sounds like would have worked better with the content protection. If I assigned a group full access rights to the shared mailbox and added the users to the group, would that allow them access to the content? Based on what you've said, I don't think so, but wanted to be sure. Second, you mentioned adding a user to a group as a way that they get rights to the content. Why is it that if the user opens Outlook on the web and opens the shared mailbox from there, they are able to view the protected email messages? If they don't have rights to access the content, I wouldn't expect it to work there either. I still have a couple of questions about this situation that I hope you can clarify.

Outlook crashes when opening shared mailbox